The United States is working to rush assistance to Mexico as it fights violent drug cartels, including equipment to help authorities track the narcotics mafia, according to the top US military officer.

"We're all working very hard to move the capabilities that are desirable to Mexico as quickly as we can," Admiral Mike Mullen told reporters by phone from his aircraft after holding talks in Mexico.

During his meetings with the country's military leadership, Mullen said he discussed how Washington could help in the battle against the powerful cartels, citing intelligence, surveillance and reconnaissance (ISR) as a crucial element.

"ISR, that kind of capability is certainly a big part of it," Mullen said, using a term that can refer to manned surveillance aircraft as well as unmanned drones.

He said the emphasis would be on sharing intelligence "but in recognition that there are additional assets that could be brought to bear across the full ISR spectrum."

With last year's death toll from drug-related violence at 5,300 as well-financed cartels orchestrate a campaign of intimidation and kidnappings, the crisis over the border has become a serious national security concern for the United States.

The visit by the chairman of the Joint Chiefs of Staff underlined US concern over the escalating violence, which experts say is fed by easy access to guns and drug profits on the US side of the border.

Mullen said the US military was ready to share tactics learned in fighting insurgent networks in Iraq and Afghanistan that he said could prove useful in Mexico's drug war.

The US military was "sharing a lot of lessons we've learned, how we've developed similar capabilities over the last three or four years in our counter-insurgency efforts as we have fought terrorist networks.

"There are an awful lot of similarities," he said.

The admiral said Mexico made no request for US troops to deploy on the northern border but authorities there were increasingly open to bolstering military cooperation with the United States, in a break with tradition.

"What I find is the military to military relationship is the best I've ever seen it," Mullen said.

As part of the US Merida Initiative that gives Mexico 1.4 billion dollars over three years to fight the growing drug mafia, Mullen said the military and other government agencies were trying to expedite funding and assistance already approved under the 2008 federal budget.

The two countries started sharing intelligence after signing an agreement in November and under the Merida Initiative the US plans to deliver helicopters, maritime surveillance aircraft and other equipment, according to the Pentagon.

During his visit to Mexico, Mullen met with the secretary of defense, General Guillermo Galvan, and secretary of the navy, Mariano Francisco Saynez, saying he had come to hear how the United States could help.

"I share their deep concern over organized crime and narco-trafficking and appreciate their vigorous efforts to improve security," Mullen said in a statement earlier.

"Mexico is not just our neighbor. She is our good friend and a nation with whom we share a long border and shared responsibilities. I come here to listen and to learn, and to try to see the security challenges we both face through the eyes of Mexican leaders."

The two countries have traded accusations over failures in the drug war, with Mexican President Felipe Calderon taking offense at a US government report blaming corruption in his country.

Calerdon hit back in an interview with AFP this week, saying corruption in the United States was also fueling the crisis.

The Mexican president has cracked down on cartels since taking office in 2006, often with bloody repercussions as Mexico battles a surging drug trade and drug-linked violence.

Before Mexico, Mullen travelled to Brazil, Chile, Peru and Colombia in a week-long tour of Latin America.